Manpages - CURLOPT_DEBUGFUNCTION.3

CURLOPT_DEBUGFUNCTION - debug callback

  #include <curl/curl.h>

  typedef enum {
    CURLINFO_TEXT = 0,
    CURLINFO_HEADER_IN,    /* 1 */
    CURLINFO_HEADER_OUT,   /* 2 */
    CURLINFO_DATA_IN,      /* 3 */
    CURLINFO_DATA_OUT,     /* 4 */
    CURLINFO_SSL_DATA_IN,  /* 5 */
    CURLINFO_SSL_DATA_OUT, /* 6 */
    CURLINFO_END
  } curl_infotype;

  int debug_callback(CURL *handle,
                     curl_infotype type,
                     char *data,
                     size_t size,
                     void *userptr);

  CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DEBUGFUNCTION,
                            debug_callback);

Pass a pointer to your callback function, which should match the prototype shown above.

CURLOPT_DEBUGFUNCTION(3) replaces the standard debug function used when CURLOPT_VERBOSE(3) is in effect. This callback receives debug information, as specified in the type argument. This function must return 0. The data pointed to by the char * passed to this function WILL NOT be null-terminated, but will be exactly of the size as told by the size argument.

The userptr argument is the pointer set with CURLOPT_DEBUGDATA(3).

Available curl_infotype values:

CURLINFO_TEXT

The data is informational text.

CURLINFO_HEADER_IN

The data is header (or header-like) data received from the peer.

CURLINFO_HEADER_OUT

The data is header (or header-like) data sent to the peer.

CURLINFO_DATA_IN

The data is protocol data received from the peer.

CURLINFO_DATA_OUT

The data is protocol data sent to the peer.

CURLINFO_SSL_DATA_OUT

The data is SSL/TLS (binary) data sent to the peer.

CURLINFO_SSL_DATA_IN

The data is SSL/TLS (binary) data received from the peer.

NULL

All

  static
  void dump(const char *text,
            FILE *stream, unsigned char *ptr, size_t size)
  {
    size_t i;
    size_t c;
    unsigned int width=0x10;

    fprintf(stream, "%s, %10.10ld bytes (0x%8.8lx)\n",
            text, (long)size, (long)size);

    for(i=0; i<size; i+= width) {
      fprintf(stream, "%4.4lx: ", (long)i);

      /* show hex to the left */
      for(c = 0; c < width; c++) {
        if(i+c < size)
          fprintf(stream, "%02x ", ptr[i+c]);
        else
          fputs("   ", stream);
      }

      /* show data on the right */
      for(c = 0; (c < width) && (i+c < size); c++) {
        char x = (ptr[i+c] >= 0x20 && ptr[i+c] < 0x80) ? ptr[i+c] : '.';
        fputc(x, stream);
      }

      fputc('\n', stream); /* newline */
    }
  }

  static
  int my_trace(CURL *handle, curl_infotype type,
               char *data, size_t size,
               void *userp)
  {
    const char *text;
    (void)handle; /* prevent compiler warning */
    (void)userp;

    switch (type) {
    case CURLINFO_TEXT:
      fprintf(stderr, "== Info: %s", data);
    default: /* in case a new one is introduced to shock us */
      return 0;

    case CURLINFO_HEADER_OUT:
      text = "=> Send header";
      break;
    case CURLINFO_DATA_OUT:
      text = "=> Send data";
      break;
    case CURLINFO_SSL_DATA_OUT:
      text = "=> Send SSL data";
      break;
    case CURLINFO_HEADER_IN:
      text = "<= Recv header";
      break;
    case CURLINFO_DATA_IN:
      text = "<= Recv data";
      break;
    case CURLINFO_SSL_DATA_IN:
      text = "<= Recv SSL data";
      break;
    }

    dump(text, stderr, (unsigned char *)data, size);
    return 0;
  }

  int main(void)
  {
    CURL *curl;
    CURLcode res;

    curl = curl_easy_init();
    if(curl) {
      curl_easy_setopt(curl, CURLOPT_DEBUGFUNCTION, my_trace);

      /* the DEBUGFUNCTION has no effect until we enable VERBOSE */
      curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);

      /* example.com is redirected, so we tell libcurl to follow redirection */
      curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);

      curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
      res = curl_easy_perform(curl);
      /* Check for errors */
      if(res != CURLE_OK)
        fprintf(stderr, "curl_easy_perform() failed: %s\n",
                curl_easy_strerror(res));

      /* always cleanup */
      curl_easy_cleanup(curl);
    }
    return 0;
  }

Always

Returns CURLE_OK

*CURLOPT_VERBOSE*(3), *CURLOPT_DEBUGDATA*(3),